package main

import (
	"fmt"
	"runtime"
)

func main(){
	fmt.Print("Go runs on ")
	switch os := runtime.GOOS; os{
	case "darwin" :
		fmt.Println("OS X.'")
	case "linux" :
		fmt.Println("Linux.")
	default:
		fmt.Printf("%s\n",os)
	}
}